India, Dec. 26 -- In line with forecasts, air quality in the national capital began a steady decline on Thursday as winds speeds decreased over the course of the day. It is expected to return to "very poor" by Saturday and stay there over the subsequent days.

Thursday began on a relatively better note with the air quality index (AQI) staying in the "poor" quality, a day after strong winds dramatically improved air quality, ending a 14-day streak of "very poor" and "severe" air.

The 24-hour average AQI on Thursday was recorded at 234 (poor) at 4pm, according to the daily national bulletin by the Central Pollution Control Board (CPCB), down from the 271 (poor) recorded at the same time a day earlier. However, the average AQI over the cour...